Pediatric diarrhea is a common disease in children characterized by an increase in stool frequency and specific stool shapes, caused by multiple pathogens and factors. Common tests for children with diarrhea start with routine stool tests. Stool culture is meaningful for identifying the pathogens causing diarrhea, and the latex agglutination test has diagnostic value for viral gastroenteritis. The stool-reducing sugar test primarily assesses malabsorption of disaccharides, lactose intolerance, etc. Counting and classifying white blood cells mainly clarify the presence of bacterial infections. Since diarrhea often accompanies electrolyte disturbances and dehydration, biochemical blood tests are necessary, and sometimes, X-rays of the abdominal plain film, ultrasound, endoscopy, and other examinations are needed.